Enhanced 911 (or E911) service is a feature of the 911 emergency-calling system that automatically associates a physical address with a calling party's Automatic Number Identification (ANI). The enhanced 911 service provides emergency responders with the location of the emergency without the calling party having to provide it. A final destination of a 911 call (e.g., where the 911 operator is located) is referred to as a Public Safety Answering Point (PSAP). A calling party number (CPN) may be used to determine the ANI associated with the calling party. The ANI may be used to look up an address of the calling party, associated with the ANI, in a third party Automatic Location Identification (ALI) database that is secure and separate from the public telephone network. The determined address of the calling party may be used to locate the closest PSAP to the calling party in the emergency situation. The PSAP may receive emergency (or 911) calls and associated address information, and may respond to the emergency accordingly.
In 2005, the Federal Communications Commission imposed obligations on voice over Internet Protocol (VoIP) service providers (VSP) to enable E911 services to their VoIP subscribers. As a result, VoIP subscribers must register their locations with the VSP for storage in regional ALI databases. Now, when a VoIP subscriber makes a 911 call, the VSP (or a positioning server) and the PSAP can query the regional ALI databases to assist in accurate PSAP termination and to provide an emergency operator with the VoIP subscriber's location and callback number. Such an emergency calling scenario is simplistic, and several complexities can be introduced into the scenario. For example, the VoIP subscriber may become mobile, and/or the VSP may not have the resources to route the emergency call to the proper PSAP and may utilize another VSP's network to complete the emergency call. There may be numerous factors that can cause route failures or inaccurate location identification being provided to the PSAP.